Method for control of yarn processing equipment

ABSTRACT

A method for starting or stopping each of at least two separately controllable roll-sets ( 22, 26, 34, 56 ) used for processing a yarn (Y) in a stretch-break process, each roll-set comrpising at least two rolls, the method is characterized by the step of each roll-set, changing the speed of each roll from an initial condition to a steady state condition in accordance with a predetermined sequence and in coordination with a change in speed of at least one of the other rolls, such that simultaneous complete breakage of a yarn (Y) being processed in a stretch-break process is minimized.

FIELD OF THE INVENTION

The present invention relates to control of yarn processing equipment ina stretch-break process and in particular to a method for starting theprocess in a coordinated manner.

BACKGROUND

The textile industry utilizes multi-positional commercial spinningmachines capable of winding multiple spindles of identical product. Onetype of commercial yarn producing machine, known as a ring spinningmachine, directly produces a staple yarn. The production throughput ofsuch a machine is relatively limited.

Another direct spinning apparatus, which for the purpose of thisapplication is referred to as a “stretch-break” apparatus, improvesthroughput by producing staple yarn directly from a multi-filament yarnfeed in a continuous operation. Shown within the dotted box in FIG. 1 isa schematic view of the functional and enabling elements of a singleposition 12A of a stretch-break apparatus generally represented byreference character 10. One or more additional stretch-break positions12B, 12C, . . . 12N, each identical to position 12A, may be provided todefine a multi-position apparatus 10. The apparatus 10 is disclosed andclaimed in co-pending application Ser. No. 09/979,808, publishedinternationally on Dec. 21, 2000 as WO 0077283.

Throughout the following description of the stretch-break apparatus itshould be appreciated that each roll in a position may be implemented asmultiple rolls, with or without associated nip rolls. It should also beunderstood that the pressure exerted by the nip rolls may be controlled,either manually or by an associated control device.

The position 12A includes a drawing and annealing zone 20, a first breakzone 30, a second break zone 40 (also known as a re-break zone), and aconsolidation zone 50 connected in series between a continuous supply 16of yarn Y and a windup zone 60.

The yarn supply 16 may include an unwinder 18 driven by enabling unwindcontroller 19, as shown, or another suitable yarn supply device. Theunwind controller 19 may be implemented by a braking mechanism or anunwind motor to control the tension of the yarn Y fed from the unwinder18.

The drawing and annealing zone 20 is defined between a roll 22 and adriven roll 26 and includes a hot plate 24. The roll 22 includes anenabling heater 22H and the hot plate 24 includes an enabling heatingelement 24H. The roll 26 may also include an enabling heater 26H. As iswell known, to impart draw action, driven roll 26 must rotate at ahigher surface speed than the surface speed of the heated roll 22. Theratio of the surface speed of roll 26 to the surface speed of roll 22 istermed “draw ratio”.

The first break zone 30 is defined between rolls 26 and 34, and thesecond break zone 40 is defined between rolls 34 and 42. The ratio ofthe surface speed of roll 34 to the surface speed of roll 26 is termed“stretch-break ratio”, while the ratio of the surface speed of roll 42to the surface speed of roll 34 is termed “re-break ratio”. An optionaljet 32 with enabling air supply 32S may be included in the first breakzone 30. The second break zone 40 may include an optional jet 36 with anassociated enabling air supply 36S.

The consolidation zone 50 is defined between rolls 42 and 56 and mayinclude one or more consolidation jets 52 and its enabling air supply52S. The consolidation device may also be a mechanical or other fluiddevice designed to consolidate the yarn Y. The ratio of the surfacespeed of roll 56 to the surface speed of roll 42 is termed“consolidation ratio”.

The windup zone 60 includes a traversing winder 62 for collecting thefinished staple yarn S on a bobbin B. The winder 62 has an associatedenabling winder and traverse drives 62D, 62T. A waste jet 58 and itenabling-air supply 58S may directly precede the winder 62 to facilitatestringing. The ratio of the surface speed of winder 62 to the surfacespeed of roll 56 is termed “Take Up Tension” (in the table of FIG. 4).

Individual rolls that sequentially contact the yarn Y during thestretch-break process may be paired into operational roll-sets. Thus,rolls 26, 34 may define a first roll-set 30S, rolls 34, 42 may define asecond roll-set 40S, and rolls 42, 56 may define a third roll-set 50S.Each roll 22, 26, 34, 42, and 56 has an associated enabling drive motor23, 27, 35, 43, and 57 respectively.

Alternatively, as seen in FIG. 1A, the roll 34 may be functionallyimplemented by multiple rolls, such as dual rolls 34A, 34B. Similarly,roll 42 may be functionally implemented by multiple rolls, such as dualrolls 42A, 42B. In such an alternative configuration rolls 26, 34A;rolls 34B, 42A; and rolls 42B, 56 may define operational roll-sets 30S′,40S′, 50S′, respectively. Rolls 34A, 34B, 42A, and 42B have associateddrive motors 35A, 35B, 43A, and 43B respectively.

In operation, yarn Y comprised of filaments F is introduced into thedrawing and annealing zone 20. Within the drawing and annealing zone 20the yarn Y is heated to an annealing temperature by the combination ofthe heater 22H within the heated roll 22 and the hot plate 24. The firstroll 22 in the drawing and annealing zone 20 grips the incomingfilaments F and the second roll in the operational roll-set (i.e., roll26) draw-stretches the same. The surface speed of roll 26 may be setrelative to the surface speed of roll 22 to draw the heated yarn Y, ifdesired, to obtain desired tensile properties.

The annealed yarn Y passes into the first break zone 30. During steadystate operation, the first roll 26 in the break zone 30 grips theannealed filaments and the second roll in the operational roll-set,i.e., roll 34 (FIG. 1) or roll 34A (FIG. 1A), as the case may be,draw-stretches them until all of the filaments F break in a randommanner. The filaments F may be further broken in the second break zone40 located downstream from the first break zone 30. An optional jet 36may be used to control ends of filaments broken in the first break zoneto prevent roll wraps.

The yarn Y is then consolidated in the consolidation zone 50 to form astaple yarn S. The staple yarn S is wound on the bobbin B undercontrolled tension and traverse speed by the winder 62.

The stretch-break process as implemented in the apparatus 10 isparticularly difficult to start, since the dynamic stretching andbreaking properties of a yarn differ at various speeds and differ fromits static properties. The goal of the stretch-break process is to breakall of the filaments randomly in both time and location. In theapparatus of FIG. 1 all the filaments are broken randomly in the firststretch-break zone 30, and those broken filaments are re-broken randomlyin the second re-break zone 40. Aggressive starting could result insimultaneous complete breakage of all filaments in either zone,resulting in loss of string-up of the yarn through the apparatus andgeneration of waste product.

Startup is particularly complicated by the interaction of processparameters. For instance, the stretch-break tolerance (i.e., thebreakage of some filaments without complete breakage) of the yarn isaffected by the annealing temperature, which changes throughout startup.The stretch-break tolerance of the yarn also changes significantly asroll speeds, and the relative speed ratio of rolls in a given roll-set,vary throughout startup. Jet parameters, particularly operatingpressure, affect the degree of fiber entanglement, and windingparameters, such as winding tension, also affect the yarn'sstretch-break tolerance.

In view of the foregoing is believed to be beneficial to provide acomputer-implemented method for controlling the transition from aninitial to a steady state condition of a single or multi-positionstretch-break process that minimizes the possibility of complete yarnbreakage and waste. It is believed of further advantage to be able tocontrol the process. parameters in accordance with a predetermined“recipe” tailored to each individual yarn. As used herein the term“recipe” is a predetermined sequence of changes of operationalparameters for the various enabling elements in each position of thestretch-break apparatus. For example, a given recipe will specifysequential changes in the speed of each roll in coordination with thechange in speed of at least one other roll (i.e., the ratio of speeds ina given roll-set), the temperature of each heater or heated roll, theoperating parameter (i.e., pressure state) of associated jet(s), and thewinder tension, to cause a processing position to transition from astopped or initial condition to a steady state operating condition. Thetransitions of parameters may be varied in a step-wise or continuousmanner.

SUMMARY OF THE INVENTION

This invention comprises a computer-implemented method and program forstarting each of at least three separately controllable roll-sets usedfor processing a yarn Y in a stretch-break process. Each roll-setcomprises at least two rolls. Under the method of the present invention,for each roll-set, the speed of each roll is changed from an initialcondition to a steady state condition in accordance with a predeterminedsequence and in coordination with a change in speed of at least one ofthe other rolls, such that complete breakage of a yarn Y being processedin a stretch-break process is minimized.

The start up sequence of the method may be practiced in two manners. Inthe first manner the speed of each roll is changed in at least twodiscrete steps to achieve a steady state set of roll speeds. In thesecond the speed of each roll is continuously changed to the steadystate roll speeds.

The predetermined sequence is created by the steps of:

-   -   a) selecting a candidate speed for each roll;    -   b) validating the candidate speed for each roll against        predetermined operability criteria; and    -   c) for speeds that meet the operability criteria, setting the        speed for each roll.

BRIEF DESCRIPTION OF THE FIGURES

The invention may be more fully understood from the following detaileddescription taken in connection with the accompanying drawings, whichform a part of this application, and in which:

FIG. 1 is a schematic view of one position within a multi-positionstretch-break apparatus of the prior art while FIG. 1A is a schematicview of a modification thereof;

FIG. 2 is a detailed block diagram of a computer system and associatedcontroller for executing a program in accordance with the method of thepresent invention to control each position;

FIG. 3 is an example of a screen display generated by the graphical userinterface of the computer system of FIG. 2; and

FIG. 4 is a table illustrating an example of a multi-step process recipein accordance with the present invention.

DETAILED DESCRIPTION

Throughout the following detailed description similar referencecharacters refer to similar elements in all figures of the drawings.

FIG. 2 is a detailed block diagram of a control system 110 comprising acomputer 112 and associated controller(s) 118 for executing a program inaccordance with the method of the present invention to control eachposition 12A through 12N of the multi-position stretch-break apparatus10 in accordance with a predetermined recipe. The control system 110 maybe implemented using a standard desk-top personal computer 112 and oneor more commercially available Programmable Logic Controllers (PLCs)118.

The computer 112 comprises a central processing unit (CPU) 124, a memory126, an operator display 128, a keyboard 142 and mouse 144 for operatorinput, an input-output interface 130 and an associated storage device116 connected by a data and control bus 122. The memory 126 may beimplemented as random access memory (RAM) or another suitable memorydevice and may be partitioned into memory units 152A, 152B, . . . 152F.The operator display 128 includes a cathode ray tube (CRT), a LiquidCrystal Display (LCD) or some other device for displaying a graphicaluser interface 114 whereby an operator communicates with the computer112 using the keyboard 142 and the mouse 144. A visual graphic,generated by the graphical user interface 114, for a single position isshown in FIG. 3.

Suitable cable assemblies 120 implement a bus network to connect thecomputer 112 with each controller 118 using any standard bus protocol.Controllers 118 each comprise a central control unit 118C and associatedinput-output (I/O) interfaces 118-1, 118-2, 118-3, 118-4, 118-5. EachI/O interface is in turn connected by cable assemblies 200 to thecontrol devices 210-250. Each control device 210-250 is associated withrespective enabling elements for a single position 12A-12N.

As shown, I/O interface 118-1 is connected to a motor inverter unit 210,in turn connected to drive motors 23, 27, 35, 43, 57. The I/O interface118-2 is connected to heater control 220, which is in turn connected toheaters 22H and 24. I/O interface 118-3 is connected to jet control 230,which is in turn connected to jets 32, 36, 52, 54, and 58. I/O interface118-4 is connected to yarn supply tension control 240, which is in turnconnected to unwind controller 19. I/O interface 118-5 is connected towinder control 250, which is in turn connected to winder drive 62D andwinder traverse 62T. It should be appreciated that a multi-channel PLCcapable of interfacing the various enabling elements for two or morepositions 12A-12N of the apparatus 10 may be employed.

Having described the physical elements and control system architecture,the operation of the method of the present invention that permits eachposition 12A-12N to be operated independently, using an individual andcompletely different process recipe which is downloaded to controller118, may now be discussed.

The present invention stores the commands that implement a processrecipe in the computer memory 126. When these commands are executed thecontrol system 110 causes the position to perform either a multi-stepsequence or a continuous sequence.

Tables of predetermined operability criteria (i.e., operational limits)for various parameters are stored in the computer memory. An example ofan operability criterion is the maximum allowable stretch ratio at agiven temperature for a particular type yarn Y. The predeterminedoperability criteria may be experimentally determined by incrementallychanging roll-set speeds and the resulting roll speed ratios todetermine operability limits for a given yarn product that will permitachieving the desired steady state running condition.

A recipe for a given yarn product can be developed by the operator.Various candidate parameters for each operating condition are selected.Each candidate parameter is validated against its associatedpredetermined operability criteria. If the candidate parameter satisfiesthe operability criteria the parameter is entered into the recipe. Ifthe candidate parameter does not satisfy operability conditions thecandidate parameter is denied entry into the recipe. Completed recipes,shown as memory segments 154A-154F may be saved using conventionalcomputer file storage techniques.

Since yarns made of different filaments (i.e., different deniers ordifferent materials) may have completely different physicalcharacteristics, process recipe programming flexibility is critical.Each yarn type or combination of yarn types performs differently in thedrawing and annealing, break, re-break, consolidation and windup zones(20-60 of FIG. 1). In a multi-step recipe each step in the recipeincrementally changes the parameters in one of more zones. Eachincremental step changes roll speed ratios in a coordinated manner untiloperational speeds are achieved. In a similar manner, a continuousrecipe gradually increases changes roll speed ratios continuously (whichmay be approximated by incrementing speeds in many very small steps)until operational speeds are achieved.

The method of the present invention may be implemented using the systemcontrol device 110 by downloading a recipe from the desktop computer 112to the controller 118 associated with a given position. The systemcontrol device will facilitate a plurality of multi-step or continuouslyvarying process recipes to be written, modified and stored. The operatorcan select from pre-determined multi-step process recipes stored in thememory 126 (or storage device 116) and download the selected recipe toany one controller 118 associated with a yarn processing position (suchas 12A) or group of positions (such as 12A-12C). This download processis a transfer of recipe data from the system computer 112 to a dedicatedpositional programmable logic controller (PLC) 118, thus freeing thecomputer 112 for other tasks.

The PLC 118 then controls: the associated motor inverter unit 210 tocontrol drive motors 23, 27, 35, 43, 57; the heater control 220 tocontrol heaters 22H and 24H; the jet control 230 to control jets 32, 36,52, 54, and 58; the yarn supply tension control 240 to control unwindcontroller 19; and the winder control 250 to control winder drive 62Dand traverse drive 62T.

Once the data is distributed to the selected control device (210-250)associated with a particular position, that position (such as 12A) canoperate independent of the system control device 110 and independent ofother surrounding positions (such as 12B or 12C). Since each position12A-12N can potentially operate with a different multi-step processrecipe a separate local readout/operator interface 214A-214N (FIG. 1) isprovided for each position 12A-12N. This local readout 214 will enablethe operator to control a position and monitor all of the uniquepositional specific data as well as display positional and system faultmessages.

It should be noted that recipes are not specific to just motor speeds.Recipes also include operational parameters such as drawing andannealing zone heater temperatures, as well as pressure settings foraspirators, consolidation jets and nip rolls (not shown). Recipes canalso include winder-specific parameters such as helix angle, traverselength, package pressure and package length or diameter. Automatic stepstring-up may also be accommodated in a recipe. This can be done byproviding a specified time for each step to operate beforeautomatically. progressing to the next sequential step.

Using the graphical display generated by the user interface 114, shownin FIG. 3, new recipes can be developed. The graphical display haswindows associated with various icons that pictorially representhardware elements. Each window represents an operating parameter of anenabling element for a particular step in a recipe. As may beappreciated by viewing the list in the upper left corner of the display,a recipe of up to ten steps may be accommodated. If the candidateparameter satisfies operability criteria the parameter is entered intothe new recipe. If the candidate parameter does not satisfy operabilitycriteria the operator is alerted (such as by a color change or flashingwarning) and the candidate parameter is denied entry into the recipe.

A multi-step process recipe, shown as steps 1 through 6 in the top rowof the table, is tabularized in FIG. 4. The operating parameters areidentified in the left column of the table. Each step in the recipe canbe created or modified through the use of the graphical interface 114.FIG. 3 shows the operating parameters corresponding to step 6 of therecipe of FIG. 4. Calculated roll speeds are displayed based on recipeand step specific ratios. The roll speed of the next step is coordinatedwith the previous roll speed by multiplying the previous roll speed bythe step specific ratio. Therefore by entering the first roll speed orthe last roll speed and all zone ratios, all other associated rollspeeds can be calculated using a Reference Rollset Selection routine.

The Reference Roll-set Selection routine allows roll-set speedcalculations to be started from roll 1 (heated roll 22 of FIG. 1)forward or from roll 5 (roll-set 56 of FIG. 1) backward. This enables anoperator to design a step specific recipe by specifying a number ofparameters:

1) specifying a required starting speed, with the other speeds beingcalculated, or specifying a required ending speed with the other speedsbeing calculated;

2) specifying either a final yarn package diameter or package length maybe entered (If a value is entered into both, the first to be achievedduring operation becomes the operative parameter resulting in a packagedoff);

3) specifying the acceleration and deceleration time, in seconds, whichrefers to step-specific time for motors to accelerate or decelerate tothe next or previous step speed, respectively. The following calculationis required to determine motor frequency acceleration:Frequency Acceleration(Hz/sec)=(Freq_(final)−Freq_(init))/(Accel Time)

The precision of this calculation must be at least 0.1% (i.e., 10⁻³)since all rolls must accurately achieve their final speeds to maintainthe desired ratio. This gradual stepping of process ratios in thedrawing and annealing, break, re-break, consolidation and windup zonesprovides the necessary easing of the feed material to the final processspeed. These ratio steps result in a specific recipe that is unique to aspecific type yarn Y.

In addition to operability criteria, safety criteria for the specifichardware of each position are stored in a system database. Safetylimits, such as maximum motor speeds, are entered as a system managementfunction and their values are stored in the system database. If acalculated roll speed falls above a system safety limit the operator isalerted via a different graphic color change of the specific roll icon.Thus a selected parameter is validated against predetermined safetycriteria as well as operability criteria before the parameter is inputinto a recipe. The zone ratio, or initial speed is then adjusted toachieve a safe roll speed.

A background monitoring routine, resident in the system computer 112,periodically issue data requests to each positional device to ascertainthe state of machine operation via the bus network 120. A log file maybe created if desired by system computer 112 to record this data. Sincethe same bus is used to download recipes to positions, monitoring issuspended during a recipe download to maintain the integrity of data.When the recipe download is complete monitoring is resumed.

Those skilled in the art, having benefit of the teachings on the presentinvention as hereinabove set forth, may effect modifications andextensions thereof. Such modifications and extensions are to beconstrued as lying within the scope of the present invention as definedby the claims appended hereto.

1. A method for starting or stopping each of at least two separatelycontrollable roll-sets used for processing a yarn Y in a stretch-breakprocess, each roll-set comprising at least two rolls, the methodcomprising the step of: for each roll-set, changing the speed of eachroll from an initial condition to a steady state condition in accordancewith a predetermined sequence and in coordination with a change in speedof at least one of the other rolls, such that simultaneous completebreakage of a yarn Y being processed in a stretch-break process isminimized.
 2. The method of claim 1, wherein the speed of each roll ischanged to the steady state in at least two discrete steps.
 3. Themethod of claim 1, wherein the speed of each roll is changed to thesteady state in a continuous manner.
 4. The method of claim 1 whereinthe initial condition is a stopped condition.
 5. The method of claim 1wherein each roll-set is comprised of each pair of adjacent rolls thatsequentially contact the yarn Y.
 6. The method of claim 1 wherein duringthe stretch-break process a yarn Y is annealed, the method furthercomprising the step of selecting at least one annealing temperature. 7.The method of claim 1 wherein the stretch-break process includes atleast three rolls (26, 34, 56), and wherein the predetermined sequenceis created by the steps of: a) selecting a candidate speed for each ofthe three rolls; b) validating the candidate speed for each roll againstpredetermined operability criteria; and c) for speeds that meet theoperability criteria, setting the speed for each of the three rolls. 8.The method of claim 7 wherein each roll-set is comprised of each pair ofadjacent rolls that sequentially contact the yarn Y.
 9. The method ofclaim 7 wherein the stretch-break process includes at least one jet orconsolidation device (32, 36, 52), the method further comprising thestep of: selecting at least one operating parameter for the jet.
 10. Themethod of claim 9 wherein during the stretch-break process a yarn Y isannealed, the method further comprising the step of selecting at leastone annealing temperature.
 11. The method of claim 9 wherein the jetoperating parameter comprises an operating pressure and wherein theoperating pressure is selected in at least two discrete steps.
 12. Themethod of claim 11 further comprising the step of: changing theoperating pressure to each of the two pressure steps in coordinationwith the change in speed of at least one of the rolls.
 13. The method ofclaim 9 wherein the jet operating parameter comprises an operatingpressure and wherein the operating pressure is selected as a continuousrange of pressures.
 14. The method of claim 13 further comprising thestep of: changing the operating pressure through the range incoordination with the change in speed of at least one of the rolls. 15.The process of claim 8 wherein the stretch break process includes awinder operable to collect the yarn under tension on a bobbin, themethod further comprising the step of selecting the tension imposed onthe yarn by the winder.
 16. The process of claim 8 wherein the candidateoperating speed is selected using a graphic display interface, theinterface displaying a diagram of the process and having windows forentry of the operating speed.
 17. The process of claim 16 where eachpredetermined operability criteria is compared to each candidateoperating speed entry and the results of the comparison is displayed ina visual manner to indicate the speed meeting or exceeding thepredetermined operability criteria.
 18. The process of claim 11 whereinthe candidate operating pressure is selected using a graphic displayinterface, the interface displaying a diagram of the process and havingwindows for entry of the operating pressure.
 19. The process of claim 18where each predetermined operability criteria is compared to eachcandidate operating pressure entry and the results of the comparison isdisplayed in a visual manner to indicate the pressure meeting thepredetermined operability criteria.